/Engine/Source/Runtime/Engine/Public/Animation/NamedValueArray.h
Helper function Uses a simple 'tape merge' Performs an operation per-element on the two value arrays. Writes result to InOutValueArray0. InValueArray0 will be the union of the two value arrays after the operation is completed (i.e. new elements in InValueArray1 are added to InValueArray0) Performs a simple copy for each element
template<typename AllocatorTypeResult, typename ElementType, typename AllocatorTypeParam> static void Union ( [TNamedValueArray](API\Runtime\Engine\Animation\TNamedValueArray)< AllocatorTypeResult, ElementType > & InOutValueArray0, const [TNamedValueArray](API\Runtime\Engine\Animation\TNamedValueArray)< AllocatorTypeParam, ElementType > & InValueArray1 )